mount -- only mounts the database and does not open it, here only
fixed tables and views (V$) can be seen. nomount -- only starts up the instance.

To shutdown Oracle

SVRMGR> shutdown [normal | immediate | abort] normal -- waits for all the users to log out before shutting down oracle immediate -- shutdown down the database, uncommited data are lost abort -- never user this as the database will need recovery when it
starts up the next time.

If the system appears to hang when a shutdown is given Please check for any user who
has logged on to Oracle. The database will not shutdown until all the users have logged
out.To overcome this the DBA can issue

SVRMGR> shutdown immediate

This however does not save the uncommited transaction.For the query to see if there are
any users still logged on to Oracle look Helpful Queries

On starting up Oracle does the following in orde

r

Starts the instance (ORACLE_SID)
Mount the database
Opens the database to the users